WiFi technology in accordance with the standard IEEE 802.11a/b/g or 11n is currently the most used technology for broadband wireless transmission in a domestic environment.
The standard IEEE 802.11n provides some improvements with respect to IEEE 802.11a/b/g standards. Notably this last authorises the use of MIMO (Multiple Input Multiple Output) technology which is a multi-antenna technique enabling improvement of the bitrate of transmissions and of their robustness in an environment, such as the domestic environment, that is dominated by interferences.
The standard IEEE 802.11n operates in the band 2.4 to 2.5 GHz and the band between 4.9 to 5.9 GHz. These two bands are called the 2.4 GHz band and the 5 GHz band in the remainder of the description. Currently communication terminals exist that operate simultaneously in both of these bands. For example, a terminal of this type is described in the French patent n° 2 911 739, in the name of THOMSOM Licensing.
A wireless communication terminal operating in the 2.4 GHz and 5 GHz bands is thus able to simultaneously receive and/or transmit a signal in the 2.4 GHz band and a signal in the 5 GHz band. In general, the 5 GHz band is used for the transmission of video and the 2.4 GHz band is used for the transmission of data.
To be able to function simultaneously in the 5 GHz band and in the 2.4 GHz band, the communication terminal solutions typically retained are constituted of front-end modules (FEM) associated with separate antennas and interfaces via RF circuits to the baseband digital circuit operating in the corresponding frequency bands.
As is known, the front-end modules comprise power amplifiers to amplify the signals to be transmitted.
In standard systems, there is one power amplifier per transmission path. However, power amplifiers use a lot of energy. In addition, the modulations implemented in systems using MIMO technology require power amplifiers with very good linearity, which translates as poor efficiency.
However the proliferation of the number of user terminals requires that the energy consumption of these terminals is optimised. Currently, the main techniques implemented to reduce the consumption of user terminals are either using standby or the reduction of energy emitted and radiated via the antennas by reduction of the radio frequency power at the input of the power amplifiers. However, the power amplifier functioning in class A, its polarisation point is not modified and the power dissipated by the components remains high whatever the power of the signal at input. To overcome these problems, various solutions have been proposed and notably that described in the patent application US2003/0162513 A1.